A crossed roller bearing is, as is known, provided with inner and outer rings, an annular roller raceway that has a rectangular cross-section and is formed between the rings, a plurality of cylindrical rollers inserted rollably into the roller raceway so that they are alternately orthogonal with each other in the circumferential direction of the raceway. In a crossed roller bearing having an integral inner ring and an integral outer ring, a roller insertion groove or roller insertion hole is formed in the inner ring or outer ring in order to insert the cylindrical rollers into the roller raceway. The roller insertion groove or hole is sealed by a plug after the cylindrical rollers have been inserted. Crossed roller bearings having an inner ring formed with a roller insertion groove are proposed in Patent documents 1 and 2.